Personally I think that we should expand upon the existing rules and skill challenges set in The Plane Above in order to mesh with the existing rules while integrating with a ship-as-creatures model for tactical combat. You'd be able to run ship-to-ship combat in an abstract manner that way, and/or do something on a minatures level. D&D is primarily about the characters and I see why WoTC went the way they did with The Plane Above, but I like my tactical game too!

These are the goals I had in mind when creating my custom ruleset:

- Allow for both an abstract combat system based on existing rules, and a more tactical feel with ships treated more or less like creatures (which is done if you look at how the 4e vehicle rules are set up).

- Make sure that all the players have something to do even when their characters don't. If there's a fleet action, give players a ship to control. If it's just one ship, let players control marines, fighter squadrons, gun batteries, etc.

- Give ships special abilities, just like players have powers.

- Give ships levels, just like players; the ship's level helps determine its item cost as well as its challenge difficulty.

- Give ships primary and secondary roles, just like monsters. That'll help figure out what ships to use to create an interesting encounter.

- Have consistent design rules applied to all ships so that the artwork and maps accurately reflect the rules used to create the ships. A balance of abstracted playability versus consistem realism will be needed to describe ships without needing a physics handbook and a CAD program.

- Use grid maps. Keep things consisten with the character game so that existing grid mats can be reused for both character and ship combat.

Just look at the stat blocks for vehicles and you'll see that they're pretty much described as critters. In another thread, I described three types of ships in terms of their stat blocks:

Mounted: represents small craft operated by 1-2 characters, such as fighters and shuttlecraft. Their powers and abilities are handed over to the pilot, and their actions are performed on the allotted actions of the controlling character.

Critter: For NPC ships, they're treated just like monsters in order to simplify bookeeping. All their actions are performed on their initiative roll. You could conceivably have more than one initiative roll; in The Mark of Prophecy, for instance, there's a two-headed aberrant that received two separate initiative rolls and sets of actions.

Hybrid: Specifically for PC ships with more than one PC aboard. It has multiple initiative rolls for each participating PC. The helmsman is considered mounted and controls ship movements as well as powers directly under his/her control. Powers under other PC control may be invoked when the PC gets a turn.

From my ship design guide:

Ship Roles

An airship or spelljammer’s purpose will largely dictate its appearance and statistics. Shipwrights should take a few moments to think upon the new design’s purpose. When converting and redesigning an existing spelljammer ship, the ship’s uses might already be known.

Primary Role

Ships use the same combat roles as monsters do and list their combat role in the top right corner of their stat block.

Artillery: Artillery ships excel at long-range combat. They fire at extended range to soften up the enemy but they are vulnerable at close range. They tend to have light armor as a result. Carriers could be considered artillery ships, with fighters as their long range weapons.

Brute: Like battleships of the line, brutes specialize in close range combat. They tend to have relatively light armor but high hit points and they employ many weapons that deliver a powerful broadside attack. These weapons are slow to recharge, however.

Controller: Controllers manipulate the battlefield or their enemies to hinder their abilities and harass them. Quori mindbender ships, with their ability to create false targets in the minds of enemy crews, are an example of a controller.

Lurker: These relatively small ships rely upon stealth to sneak up on their target, deliver a powerful blow, and then sneak back into the shadows. They hide in the terrain or use magic to conceal themselves. Their weapons tend to recharge once every few rounds. A stealth frigate would be an example of a lurker.

Skirmisher: Skirmishers use their mobility to conduct hit and run tactics. They dart in, fire their weapons, and then move away just as quickly. A skirmisher is different than a lurker in that the skirmisher’s weapons recharge faster and they lack the lurker’s ability to hide. Frigates are a good example of a skirmisher. Relatively small, they don’t pack much of a punch but when operating in squadrons to attack their target, they can overwhelm the enemy.

Soldier: Workhorses of the fleet, soldiers specialize in drawing enemy fire and protecting other ships. They’re a balance of firepower, armor, and hit points. Cruisers are good examples of soldiers. Mid-sized vessels, they patrol the skies and space, and often serve as leaders for frigate squadrons.

Secondary Role

Elite: Elite ships are like “mini-bosses” that are tougher than standard ships of the same type. They have better stats and better crew, but not necessarily better attacks.

Minion: Minions are ships that arrive in droves, deliver a nasty sting to the target, and then scurry away, but they are easily destroyed in one hit by a ship’s armaments. Fighters definitely fit the role of a minion. Any PC or NPC villain that takes command of a minion ship automatically upgrades it to elite status while aboard ship. Hence it’s a good idea to keep track of a minion ship’s hit points.

Solo: Solo ships are intended for solo combat against enemy ships. They’re much tougher than standard ships of the type, they have better stats, and their weapons do more damage.

Leader: Leader is an additional quality added to a ship that may exist in addition to a primary and secondary role. Known as a flagship, leaders command squadrons or fleets of ships and often have a special ability that grants bonuses to the stats of ships under their command.

That's good
IMHO though, PCs shouldn't be having effects that would make them act like a "second ship", as a general rule, as we want to avoid complicaiton
what I'd suggest is:

let PCs who have specific feats, improve the ship in SPECIFIC ways

A helsman who has say, the paragon feat "Spelljammer Roll", gains a daily power, immediate interrupt power, when attacked, he can roll his ship, gaining a +2 AC versus that attack.

another character has "Ballista Commander" paragon feat, effect is close burst 4, any ballista in range does +5hp damage per tier.

and so forth

only when it comes down to boarding actions do you want the PCs normal abilities ot come into play, becuse of range and complexity

instead, have players run a specific ship weapon each.
have skill challenges to gain a tactical advantage
also as said, let the PCs "take a hit" (lose a healing surge) to keep a crew member minion alive, if they wish ands other things that aid the ship, rather than be typical PC combat.
hm?

My vision of characters aboard ships is that they use their skills to do cool things in combat as a set of skill challenges (which is what's done in The Plane Above), and in a nod to the old system, they can channel powers into the helm to enhance its speed, or channel powers into weapons to enhance their effects. I suppose you could do that with feats:

Energy Boost [Spelljamming]Prerequisite: Any power with the Arcane, Divine, Psionic, or Primal keyword.Benefit: You may channel your power into any magical item with the Energizeable keyword to enhance its effects. Read the item's description to determine what benefits it gains from being energized.

Stunt Pilot[Spelljamming]Prerequisite: Dexterity 13.Benefit: When piloting a flying vessel, you may perform special maneuvers called Stunts during combat.

Stunts are like powers. Most of them are at-will.

My concern about designing specific powers and feats is that they'll potentially detract from the character-driven game. For The Thirteenth Planet, I plan to just let players expend a magical power to boost the helm or enhance a weapon, or expend a martial power to perform a Stunt. No extra feat needed, and the power expendature represents the extra concentration and energy they're using to perform something special.